Eagle-eyed daikaiju fans might notice how the eyes of larval Mothra are red in her cinematic debut, yet they turn blue in Godzilla vs. Mothra(aka Godzilla vs. the Thing in America). In fact, they stay that way for the remainder of the old school Godzilla movies).

If you look at official reference guides, Mothra is much larger than Godzilla when she appeared in Mothra and had to be scaled down for her appearances in the Godzilla franchise.